. >>> growing concern about the health of nelson mandela, who has been in the hospital for three days. officials say the 94-year-old human rights hero is doing well. but that people should keep him in their prayers. >>> gas prices down 11 cents in the past week. they're not stopping there. a gallon now almost 50 cents less than a month ago. we could see rates at $3 a gallon by christmas. >>> the argentinian-born forward lionel messi scored two goals on sunday, bringing the total for the year to 86. by the time he's done, we could be talking about the best to ever play the game. >> all right, josh, thank you so much. >>> now to the latest on the daring rescue mission in afghanistan to free an american doctor held hostage by the taliban. an american hero has died in this operation, a member of the elite s.e.a.l. team six. martha raddatz has more. >> reporter: this is what the s.e.a.l.s train to do. this raid was more challenging than the one that killed osama bin laden. this time, the goal was to bring back an american hostage alive. it was a bold and dangerous mission. u.s. and afghan